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Alert-- Chromium and cobalt data incorrect for bed sediment

07Mar2000

PLEASE FORWARD TO YOUR STAFF WHO INTERPRET/TABLE DATA ON BED SEDIMENT QUALITY

In January, Steve Frenzel (COOK Nawqa chief) and Rick Sanzolone (GD metals lab) determined that the values for cobalt and chromium in bed sediment samples had been switched. After consultation with John Briggs (NWIS) and the NWQL it was determined that this was an error that had crept into NWIS. They've taken steps to correct this, and the details are below.

The bottom line for your work is that data for these two elements in bed sediments will be reversed, and so incorrect, in any pulls you've made after mid-November 1999. This includes tables for District basic-data reports and other District and NAWQA reports. The November NAWQA data warehouse pull was prior to the switch, and so is apparently OK.

Details

Labels for two parameters (34840 and 34845) were inadvertently switched in the Dec. 1999 release of the PCD. This is due to an inconsistency between USGS and USEPA Storet parameter codes. The parameters and labels should correctly be:

34840  CHROMIUM, SEDIMENT, BOTTOM MATERIAL, < 63U, WET SIEVE, FIELD, TOTAL, UG/G
34845  COBALT, SEDIMENT, BOTTOM MATERIAL, < 63U, WET SIEVE, FIELD, TOTAL, UG/G

No data were moved from one parameter to the other when these labels were changed, so correcting the PCD should make all data analyzed before Dec. 1999 correct again in future pulls. According to John Briggs (jbriggs), a corrected PCD should be available shortly.

Values for samples that were analyzed after November 99 were loaded into the wrong parameter codes in the NWIS data base. The NWQL has a list of these samples, and will work with individual districts to help clean up these data. Contact Steve Glodt (srglodt) at the NWQL with questions on this.

An immediate concern is that these parameters are being labeled incorrectly for QW tables generated from NWIS since December. This includes tables that are being prepared for the publication of District Annual Data Reports. Given that there aren't a lot of these data in District work, the simplest and quickest fix may be to switch label headings in the affected tables.

Contact Cory Stephens (cory) or myself (dhelsel) with any other questions.

---------------------------------------------------------------
   Dennis R. Helsel                    Ph:  (303) 236-2101 x227
   Trace Element National Synthesis    Fax: (303) 236-4912
   U.S. Geological Survey
   PO Box 25046, MS-415                dhelsel@usgs.gov
   Denver, CO   80225           http://water.usgs.gov/nawqa/trace

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